This invention relates to joint prostheses particularly adapted for replacing a joint between two of the long bones of the hand such as the joint between the metacarpal and the first phalanx that articulates with the metacarpal.
The joints between elongated bones of the hand can be damaged by accident or by diseases such as rheumatoid arthritis and osteoarthritis and often need to be surgically replaced. Procedures for replacing damaged or diseased joints often have involved surgical removal of substantial portions of the bone adjacent a joint's articulating surfaces and implantation of an articulating prosthesis. The surgical procedure often involved removing not only substantial portions of bone but also of soft tissue attachments between the bony ends of the joint. This, in turn, has often required that the articulating ends of the prosthesis be fastened together in such a manner that they are not readily separated. Pivoting of the joint in the lateral (that is, in the radial/ulnar direction) was permitted in some prosthesis variations and not permitted in others, the degree of pivoting generally being independent of the degree of flexure of the fingers. A finger joint of this general type is shown in Lewis, U.S. Pat. No. 4,231,121 issued Nov. 4, 1980, which shows a prosthesis having a spherical beating surface that articulates in a spherical recess.
Certain finger joint prostheses have been provided in which the prostheses were provided with stems having articulating, opposed heads and in which the heads were permitted limited lateral pivoting movement with respect to one another. One such prosthesis is shown in White, U.S. Pat. No. 4,242,759, issued Jan. 6, 1981. The articulating heads described in the White patent contained mating ridges and troughs, the contact between the ridges and troughs varying as the joint was flexed.
It is desired to provide a prosthesis so configured and arranged that its surgical implantation does not involve substantial disruption of soft tissue connections between the articulating bones nor removal of substantial portions of the bones themselves. Desirably, such prostheses duplicate closely the articulation afforded by a natural joint.